The present invention relates to a system and method for coating the coils of electric motor or electric generator components ("components") with a resin which preferably does not require heating after application. More particularly, the present invention relates to a system, and a related method, for coating components by continuously conveying the components through successive stations so that a plurality of components may be incrementally serviced until each component is completely and properly coated with resin. Additionally, the system and related method are capable of selectively applying resin to components so that a coated component adjacent to an uncoated component will not be recoated.
Resins are often used to coat wire coils (such as in the present invention). Heatless polyester resins are capable of bonding strengths equivalent to those of traditional resins but cure by means of an exothermic chemical reaction which takes place at room temperature. Curing in this way accordingly obviates the heating and cooling stages normally required to cure traditional resins.
Elimination of heating and cooling stages provides various advantages including: energy savings, savings in coating system costs, and savings in manufacturing spacing which needs to be dedicated to the heating and cooling equipment required by traditional resin application systems. The use of heatless resins also substantially eliminates the airborne emissions associated with high temperature curing of traditional resins.
A typical cycle for coating armatures with heatless resins requires heating the wire coils to a moderate temperature within the range of 45.degree. C. to 60.degree. C., exposing the coils to a series of resin dispensers for applying progressive amounts of resin to the coils, allowing the resin to harden, and eventually aging the resin.
Preheating of the components is carried out so that the resin reaches an ideal viscosity on the component to penetrate and fill the spacings between the coil wires. The preheating stage also reduces the time required for the resin to harden. Accordingly, a precise choice of the temperature in this stage must be made, taking into account such factors as: the type of armature to be coated, the resin being used for coating, and the production rates required by the coating operation.
The preheated components are passed through a resin dispensing/coating station in which the components are coated with resin. Preferably, the components to be coated are rotated during application of the resin so that a uniform coat may be formed.
The resin coating station typically includes a plurality of resin dispensers, such as manufactured by Liquid Control Corp. of North Canton, Ohio. Each resin dispenser typically comprises a mixer tube in which resin and a catalyst are fed and mixed. The resin, such as manufactured by The P. D. George Co., St. Louis, Mo., and the catalyst are stored in separate containers and are fed by piston pumps through supply tubes to a distributor. Until they reach the outlet of the distributor, the resin and catalyst are kept apart. The resin and catalysts are only joined as they enter the mixer tube, which has a helical path which causes a highly efficient mixing operation to occur when the resin and catalyst flow together. By activating the piston pumps at predetermined and programmable time intervals, and by regulating the stroke of their pistons, a required ratio of resin and catalyst can be fed to the mixer tube to form the desired resin composite. Mixing the catalyst with the resin causes the exothermic reaction that hardens the resin to start even at room temperature.
Once the coils have been coated with resin, they can be exposed to room temperature for gelification. Gelification is a term usually used to indicate a stage in which the resin hardens to a point at which there is no further risk of dislocation caused by manipulation of the coated coil. During gelification, coated components need to be rotated to avoid accumulation in certain areas due to the force of gravity so that the resin will be uniformly distributed within and over the coils.
Once gelification has been completed, the resin undergoes a process which is typically called aging. During this process, an internal transformation of the resin, which occurs for many hours at room temperature, increases the bonding strength to that required to hold the wires together. Normally, there is no need to postpone manipulating or processing steps after coating in order for the aging stage to be complete. On the contrary, after gelification, the components can be manipulated and processed without incurring any significant risk of dislocating the resin.
In a properly coated component, the spaces between the coil wires should be substantially completely filled with resin and all air gaps between the coil wires should be substantially completely eliminated. The resin should also have a sufficient bonding strength to hold the coil wires together, which is the principle purpose of this technology.
A system for applying heatless resins should smoothly transport the components from one stage to another without much delay between stages, so that the coating process may be achieved quickly and efficiently, without allowing a preheated component to cool before reaching resin dispensers or allowing resin to harden unevenly during resin application or transfer to the gelification stage. If any delays occur at any point in the coating process, components in the midst of treatment may be rendered unusable.
Known methods for applying heatless resins present several potential disadvantages. The reaction of the resin and catalyst during mixing needs to be carefully time-controlled because after the catalyst has been added, the exothermic reaction that causes the resin to harden occurs quickly. This means that if the catalyzed resin remains in the mixer tube of the dispenser for more than a certain well-defined amount of time, the mixer tube may become blocked by the hardened resin. The blocked tube would then have to either be flushed with a volatile solvent or discarded.
Additionally, if the application of resin to the coils being coated is interrupted for more than a certain amount of time, then partial hardening may occur before the required amount of resin has been deposited on the coils. In such a case, it may be difficult to complete coating of these components by adding further resin. The resulting components will be defective and are usually a total loss without the possibility of recovery. Such a disadvantage even occurs when using traditional resins.
Finally, if a coated component cannot be removed from the coating system, and therefore reapproaches the resin dispensers for coating, any further application of resin will typically render the recoated component useless. Such a disadvantage also occurs when using traditional resins.
It therefore would be desirable to provide a system and method for applying heatless resin incrementally, successively, and continuously. The system should efficiently simultaneously process a plurality components so that an uncoated component entering the system leaves the system completely and properly coated and ready to be operated on in the next station.
It would also be desirable to provide a system and method for resin-coating which allows for complete processing of components already in the system when supply of new components is interrupted.
It would further be desirable to provide a system and method for resin-coating which selectively applies resin to uncoated components and not to coated components also in the coating system, while not causing blockage of the resin dispensers.